Modeling the Long-term Antibody Response and Duration of Immune Protection Induced by an Inactivated,Preservative-free Hepatitis A Vaccine(Healive)in Children

Objective Long-term seroprotection via the hepatitis A vaccine is essential for the prevention of disease from the hepatitis A virus(HAV).Due to documented difficulties during decade-long follow-ups after receiving vaccines,statistical-modeling approaches have been applied to predict the duration of immune protection.Methods Based on five-year follow-up data from a randomized positive-controlled trial among Chinese children(1–8 years old)following a 0,6 months vaccination schedule,a power-law model accounting for the kinetics of B-cell turnover,as well as a modified power-law model considering a memory-B-cell subpopulation,were fitted to predict the long-term immune responses induced by HAV vaccination(Healive or Havrix).Anti-HAV levels of each individual and seroconversion rates up to 30 years after vaccination were predicted.Results A total of 375 participants who completed the two-dose vaccination were included in the analysis.Both models predicted that,over a life-long period,participants vaccinated with Healive would have close but slightly higher antibody titers than those of participants vaccinated with Havrix.Additionally,consistent with previous studies,more than 90%of participants were predicted to maintain seroconversion for at least 30 years.Moreover,the modified power-law model predicted that the antibody titers would reach a plateau level after nearly 15 years post-vaccination.Conclusions Based on the results of our modeling,Healive may adequately induce long-term immune responses following a 0,6 months vaccination schedule in children via induction of memory B cells to provide stable and durable immune protection.

Safety and effi cacy of hepatitis A vaccine in children with chronic liver diseas

AIM： To study the safety and efficacy of hepatitis A vaccine （HAV） in children with chronic liver disease of various etiologies. METHODS： Eleven children with chronic liver disease and thirteen age- and sex-matched controls negative for HAV antibodies were vaccinated against hepatitis A after they gave their informed consent. Children with uncontrolled coagulopathy or signs of hepatic decompensation were excluded. The vaccine （Havrix： 720 ELISA units in 0.5 mL, from GlaxoSmithKline Biologicals） was given intramuscularly in the deltoid in 2 doses 6 mo apart. Children were tested for HAV antibodies one and six months after the ist dose and one month after the 2^nd dose. Total serum bilirubin, alanine aminotransferase （ALT）, and aspartate aminotransferase （AST） were determined immediately before and after one month of the 1st dose of the vaccine. RESULTS： Only 7 out of the 11 patients were positive for HAV antibodies after the 1^st dose of the vaccine, as compared to 100% of the controls. One month after the 2nd dose, all patients tested were positive for HAV antibodies. No deterioration in liver functions of patients was noted after vaccination. No adverse events, immediate or late, were reported by the mothers after each dose of the vaccine. CONCLUSION： Hepatitis A vaccine is both safe and effective in this small studied group of children with chronic liver disease. Given the high seroconversion rate, post-vaccination testing for HAV antibodies is not needed.

Safety and immunogenicity of lyophilized, live attenuated hepatitis A vaccine in non-human primate model

Objective To evaluate the safety and immunogenicity of lyophilized, live attenuated hepatitis A vaccine (H2 strain) in rhesus monkeys Methods Nine adult rhesus monkeys were used as experimental animals The rhesus monkeys without anti HAV were divided randomly into the aqueous vaccination group (4 rhesus monkeys), the lyophilized vaccination group (3 rhesus monkeys), and the control group (2 rhesus monkeys) Monkeys were inoculated by intramuscular injection, with control monkeys being inoculated with Minimum Essential Medium Eagle (MEM) Following vaccination, the monkeys were observed for the development of diarrhoea and other adverse side effects, such as changes in appetite, frequency of defaecation and stool consistency for seven days At the weeks 2, 3, 4, 6, 8, 10 and 12 positnoculation, the peripheral blood was collected from all animals and assayed for anti HAV and alanine aminotransferase (ALT) and aspartate aminotransferase (AST), at weeks 0, 4 and 8 postinocuation, needle biopsy specimens were taken at weeks 0, 4, 8 and 12, all monkeys were sacrificed and tissue samples were taken from liver, lung, heart, kidney and brain for pathological examination at week 12 Results Animals were immunized with a dose of 7 0 logTCID 50 /ml which is stable after freeze drying During the 12 week observation, no animals showed abnormal elevations of liver enzymes (ALT and AST) and no change in appetite or activity Two monkeys (one in the aqueous group and the other in lyophilized group) showed possible lesions at week 8 The lyophilized vaccine, in addition to eliciting an anti HAV IgG response similar to aqueous vaccine ( P >0 05), also showed IgM anti HAV response at week 2 which was not observed with aqueous vaccine Conclusions These results demonstrate that lyophilized, live hepatitis A vaccine is safe and highly immunogenic in primates, supporting its further evaluation in human clinical studies